Calibration of a hybrid sea ice model during an expedition to the Arctic

Abstract We describe the acquisition and evaluation of data during the ArcWatch II expedition into the Arctic Ocean on board of the icebreaker Polarstern. The data is used to calibrate a hybrid sea ice model that focuses on modeling the marginal ice zone, which is the transition zone between pack ice and the open ocean. We describe the experimental setup used to track the motion of individual ice floes as well as the measurement of the wind and the ocean current. In the literature, the motion of an ice floe in the free‐drift regime is often estimated by Nansen's rule of thumb, which assumes the sea ice drifts at of the wind speed, deflected up to in clockwise direction. Analyzing the first datasets, we noticed that observed small ice floes in free drift often have a larger relative angle to the wind direction. Based on numerical simulation we quantify that these larger angles are related to the geometry of larger sea ice floes in the vicinity of the observed ice floe. These large icefloes influence the ocean current, which in turn, impacts the motion of the small ice floes in the surrounding.